Diederik Hentenaar

111 Phosphoric acid in surgical peri-implantitis treatment INTRODUCTION Triggered host defense responses initiate inflammation of the peri-implant soft tissue (peri-implant mucositis), which can lead to loss of peri-implant supporting bone (peri- implantitis), and eventually, result in implant failure (Lang & Berglundh 2011). An increasing prevalence of peri-implantitis has been described in recent literature (Derks & Tomassi 2015), with current incidence ranging from 1 to 47%. A non-linear, accelerating pattern of progress is suggested for the majority of cases, with an occurring onset within 3 years of function (Derks et al. 2016). As for periodontal disease, the presence of micro-organisms is an important factor for the development of an inflammatory response in peri-implant tissue (Lindhe & Meyle 2008). In order to effectively treat the peri-implant inflammation, disruption of microbial adhesion and reduction of biofilm accumulation on the implant surface is probably of eminent importance. A number of mechanical interventions ( e.g. abrasive air powder, teflon curettes, ultrasonic devices) and chemical agents ( e.g. chlorhexidine, hydrogen peroxide) solely or in combination, have been described as methods for implant surface decontamination in both in-vivo and in-vitro studies, in both a surgical and non-surgical setting (Leonhardt et al. 2003, Máximo et al. 2009, Serino & Turri 2011, Heitz-Mayfield et al. 2012, De Waal et al. 2013, Bassetti et al. 2014, De Waal et al. 2016, Riben-Grundstrom et al. 2015). According to different reviews on in-vivo and in-vitro mechanical debridement (Esposito et al. 2012, Subramani 2012, Louropoulou et al. 2014, Schwarz et al. 2015, Ramanauskaite et al. 2016) a gold standard mechanical debridement regimen still does not exists. Possibly, the implant surface roughness and screw-shaped design of dental implants may compromise an effective mechanical intervention. Therefore, the additional use of chemical agents for implant decontamination may be advocated. Antimicrobial solutions have been studied in different clinical studies (Gosau et al. 2010, Heitz-Mayfield et al. 2012, De Waal et al 2013, De Waal et al. 2016). No superior clinical effectiveness has been shown in a single study for a specific chemical decontamination protocol (for reviews see: Ntrouka et al. 2011, Subramani 2012, Meyle 2012). However, studies using acids at low pH (< 2) have shown potentially beneficial antiseptic effects (Zablotsky et al. 1992, Dennison et al. 1994, Strooker et al. 1998, Mouhyi et al. 2000, Wohlfahrt et al. 2012, Wiltfang et al. 2012, Chen et al. 2016, Htet et al. 2016). Especially results on decontamination with phosphoric acid might be promising. Wiltfang et al. (2012) showed that surface decontamination with phosphoric acid (pH 1) in a surgical treatment protocol, resulted in complete elimination of the bacterial microflora. Also, results of a short-term clinical trial by Strooker et al. (1998) showed an instant greater reduction of colony forming units on the implant surface when using phosphoric 5